In a disk drive, such as a hard disk drive, a recording disk has circular tracks formed in its major surface and storing user data and servo data. The servo data is used for controlling the movement of a head for writing or reading operations. The servo data includes track data on the tracks, and sector data identifying sectors in the tracks.
The storage capacity of recording disks has been progressively increased in recent years. The ratio of the servo data to all the data recorded on the recording disk has increased as the storage capacity increases. There is a possibility that such increase of the servo data reduces the capacity for storing user data.
For example, when the width of tracks is reduced to provide a recording disk of a large storage capacity, head positioning accuracy needs to be increased. Therefore, the number of servo data areas in the tracks is increased and sampling frequency at which servo data is sampled is increased. Consequently, bit length for sector data increases and servo data increases.
When the number of tracks is increased to increase the storage capacity of the recording disk, bit length necessary for track data and servo data increase.